Blast furnace teardown apparatus



April 1969 J. ARMSTRONG 3,436,120

BLAST FURNACE TEARDOWN APPARATUS Filed Aug. 15, 1964 Sheet INVENTOR.JOHN ARMSTRONG ATTORNEY A ril 1, 1969 J. ARMSTRONG 3,435,120

sus'r wanes 'rmanown APPARATUS Filed Aug. 15, 1964 Sheet 2 of 5 FIG.4

INVENTOR JOHN ARMSTRONG ATTORNEY April 1969 J. ARMSTRONG 3,436,120

BLAST warmer: TEARDOWN APPARATUS Filed Aug. 15, 1964 Sheet 3 of 5 FIGSINVENTOR, JOHN ARMSTRONG ATTORNEY April 1969 J. ARMSTRONG 3,436,120

BLAST FURNACE TEARDOWN APPARATUS Filed Aug. 1:, 1964 Sheet 4 of 5 Q 1 LLm INVENTOR w JOHN ARMSTRONG BY gal- M;

O ATTORNEY A ril 1, 1969 J. ARMSTRONG BLAST FURNACE TEARDOWN APPARATUSFiled Aug. 13, 1964 Sheet J IN VENTOR. JOHN ARMSTRONG FIG. I3 BY ymfi ATTOR NE Y 3,436,120 BLAST FURNACE TEARDOWN APPARATUS John Armstrong,Michigan City, Ind., assignor to J. J.

Grady (10., Inc., Pitttsburgh, Pa., a corporation of Indiana Filed Aug.13, 1964, Ser. No. 389,432

Int. Cl. E211) 35/02 U.S. Cl. 29970 6 Claims The present inventionrelates to new improved means for removing brick or masonry linings etc.from circular structures such as iron-making blast furnaces and thelike.

A typical modern iron-making blast furnace comprises an outer steelshell lined on the inside with refractory brick having embedded thereinwater cooled coils etc. The operation of the blast furnace causes suchlinings to become worn, cracked or badly broken; and, periodically, itis necessary to tear down the furnace lining so that the furnace may berebuilt with a new lining, cooling coils etc.

The usual procedure for tearing down and removing the lining is to lowerinto the blast furnace from the top a scaffold bearing a number of men(e.g. -20) using air hammers, pickaxes and rakes etc. for manuallytearing down the lining from the shell and to remove debris from thescaffold. From time to time, the scaffold is lowered so that the men mayprogressively tear down successively lower sections of the blast furnacelining until the furnace teardown is completed. Also, since the lowerportion of a blast furnace stack is larger than the upper portion, it isnecessary to enlarge the scaffold as it is lowered in the stack, toenable the men to manually break up the furnace lining with air hammersand like manual tools. According to present practice, the scaffoldplatform is enlarged as it is progressively lowered in the blast furnaceby adding radial stringers and boards. Of course, this holds up thefurnace teardown work, besides requiring mid-air assembly which isundesirable from the safety viewpoint. In addition, the extended woodenstringers are subject to breakage; and enlargement of the platformincreases the likelihood of the scaffold tipping due to movement of men,equipment and loading of debris disposed at an increased distance fromthe platforms center of gravity.

The job of blast furnace teardown is a quite formidable one, and suchmanual procedures for teardown require the use of many laborers over aconsiderable period of time; eg according to present practice prevailingin the U.S. steel industry, it requires about 15-20 men working as abovedescribed about 72 hours continuous work to tear down a blast furnace.This is not only a slow and expensive procedure in terms of man hoursconsumed, but it results in substantial additional expense due to delayin rebuilding the furnace so that it may be returned to production.Further, undue delay may adversely affect the efiiciency of the entiresteel making plant which is dependent on the blast furnace for the pigiron used in making steel.

The problems and shortcomings of the above-discussed manual furnaceteardown system have been recognized for some time, as exemplified byU.S. patent to Putnam No. 2,710,418 proposing a power scaffold for blastfurnace teardown to eliminate manual procedures.

Accordingly, it is a primary object of the present invention to providea new improved power-operated blast furnace teardown system andapparatus for quickly and efficiently removing the linings from blastfurnaces, overcoming the shortcomings and disadvantages of prior methodsand apparatuses heretofore available and used.

It is an object of the present invention to provide a new improved blastfurnace teardown apparatus comprisatet ing a novel combination of aconventional mass-produced digging machine with a novel turntablescaffold arrangement. It is a related object to provide such a newimproved power-operated blast furnace teardown device incorporating aplatform which may be lowered by a crane into the top of a blast furnaceand thereafter progressively lowered to desired positions forprogressive teardown of the furnace lining. It is another related objectto provide such a new improved power teardown apparatus in which thecenter of gravity of the digging machine is substantially at the centerof the platform, for increased stability and to avoid dangerous tippingof the platform which might cause men or equipment to fall from it.

It is still another related object to provide a new improvedpower-operated apparatus for tearing down a blast furnace lining inwhich the load is primarily vertically imposed on the scaffoldsupporting cablesfor increased stability. It is yet another relatedobject to provide a new improved method and apparatus for tearing down ablast furnace lining which makes it possible to conduct the actualbreaking up of the furnace lining at a level approximately at or belowthe level of the platform, to prevent debris from striking men on theplatform helping the digging machine operator.

It is another object to provide a new improved poweroperated blastfurnace teardown apparatus including a scaffold having a centrallymounted digging machine with an extensible boom, whereby it isunnecessary to enlarge the platform as it is lowered into the enlargedlower sections of the blast furnace thereby avoiding the delay anddisadvantages of present teardown practices requiring such platformenlargement. It is another object of the present invention to provide anew improved poweroperated blast furnace teardown apparatus which isadapt ed for use in oversized blast furnaces.

It is still another object of the present invention to provide a novelscaffold suspension incorporating a novel cross head, platform, andcable arrangement whereby the boom of a digging machine on the platformmay swing in a circle without interference from the supporting cables,for efficient teardown operations. It is another related object toprovide an improved power teardown device incorporating a scaffoldturntable with means for locking in desired position a conventionaldigging machine having 200 swing and permitting ready reorientation ofthe digging machine for tearing down the entire circular periphery ofthe furnace.

It is still another object of the present invention to provide a novelimproved scaffold platform having removable side portions making itpossible to use the same platform for blast furnaces of different sizes,and particularly permits insertion of the platform and related equipmentthrough a smaller blast furnace throat.

It is a further object of the present invention to provide a novelimproved power-operated blast furnace teardown system and apparatuswhich enables four men to tear down a typical blast furnace in about 36hours, with an approximate 35% reduction in cost compared to prevailingmanual practices in the U.S. steel industry.

It is another object to provide such a power teardown system using aminimum of special machinery, and making it possible to quickly obtainmass-produced spare parts at low cost (in addition to minimizing cost ofdesigning and producing equipment).

The above and other objects and advantages of the present invention willbe apparent from the following description thereof with reference to theaccompanying drawings and claims.

In the drawings (wherein like parts are identified by like numerals):

FIG. 1 is an idealized diagrammatic cross section of an iron-makingblast furnace, showing in side elevation Patented Apr. l, 196%? a blastfurnace teardown device according to the present invention (in upperposition in solid line, and in lower position in dotted line);

FIG. 2 is an enlarged side elevation of part of the scaffold or platformsuspension arrangement of the present invention shown in FIG. 1;

'FIG. 2A is a top plan view of a portion of the platform suspensionmeans shown in FIG. 2 (looking down along line 2A--2A in FIG. 2)

FIG. 3 is a top plan view of the upper cross head used in the platformsuspension of this invention (looking along line 3-3 in FIGS. 1 and 3);

FIG. 4 is a side elevation of the upper cross head shown in FIG. 3;

FIG. 5 is a top plan view of the platform which supports the diggingmachine and workmen according to the present invention (looking downalong line 55 in FIG. 2), with portions of the platform surface omittedin the left half of FIG. 5 for greater clarity;

FIG. 6 is a side elevation of the platform shown in FIG. 5 (lookingalong line 66 in FIG. 5);

FIG. 7 is a vertical sectional view looking along line 77 in FIG. 5;

FIG. 8 is a partial vertical sectional view looking along line 88 inFIG. 5;

FIG. 9 is a partial vertical sectional view looking along line 99 inFIG. 5;

FIG. 10 is a side elevation view showing the device for locking thedigging machine mount bearing to locate the digging machine in desiredposition;

FIG. 11 is a partial horizontal sectional View taken along line 11--11in FIG. 10;

FIG. 12 is a side elevation and partial sectional view illustrating useof the power-operated apparatus of this invention for tearing down thelining in the upper narrower throat portion of a blast furnace;

FIG. 13 is a side elevation and partial sectional view similar to FIG.12 illustrating use of the power-operated apparatus of this inventionfor tearing down the lining in the lower wider portion of a blastfurnace, with a modification of the mount for the air hammer on the boomof the digging machine.

Referring to the drawings, particularly FIG. 1, the new improved blastfurnace teardown apparatus according to the present invention isindicated generally at 20 and is shown in connection with a more or lessconventional blast furnace 22 having an outer steel shell 24 lined withfire brick lining 26. While the bustle pipe 28, mantle 30, columns 32and tuyere 34 are shown, the other conventional parts of the furnace 22have been omitted for the purpose of clarity.

The improved teardown apparatus 20 of this invention comprises ascaffold platform 36 having a digging machine 38 rotatably mountedthereon. The platform 36 and the digging machine 38 are suspended bymeans of cables 40 from a crosshead 42. The crosshead and thus theplatform and digging machine are raised and lowered within the furnaceby the suspension means shown generally at 44.

More specifically, the suspension means 44 includes a cable or wire rope46 which is attached at one end to a suitable hoist or the like (notshown) and extends around the pulley or pulleys 48, with its other endattached to a grab ring 50. The pulleys 48 are mounted in a bracket 52attached to the blast furnace building superstructure 54. Four chains46, which are of equal length, have opposite ends secured to the grabring 50 and crosshead 42.

As shown especially in FIGS. 1, 3 and 4, the lower end of each of thechains 56 is fastened to one of four brackets 58 which are welded toupper flanges 60 of the steel I-beams '62 and 64, adjacent the endsthereof. Beams 62 and 64 form the primary members of the crosshead 42and are spliced and welded together at their midpoints,

with the intersection 66 of these beams being reenforced by plates 68.For added stability and strength, four I-beams 72, 74, 76, and 78 arewelded t9 beams 62 and 64 4 at suitable points, as illustrated. Abracket 70 may be provided for the attachment of a safety cable, notshown.

As shown particularly in FIGS. 2 and 4, beams 62 and 64 have a portionof their lower flanges 80 cut away adjacent each end, and reenforcingplates 82 are welded to each side of the web 84 above the cut-awayportion, with a hole 86 being drilled through the plates 82 and web 84for attaching the upper ends of the cables 40. Cables 40 extend betweenbeams 62 and 64 and the platform 36 to support the latter.

Alternatively, it is possible to cut away the upper flanges 60 adjacenteach end of beams 62 and 64, drill a second hole through the plates 82and web 84, and attach the lower ends of the chains 56 thereto insteadof to the brackets 58.

The lower ends of the cables 40 are attached to the ends of steelI-bearns 88 and 90 which are spliced and welded together at theirmidpoints and comprise primary members of the platform 36. Plates 92reen-force the intersection 94 of beams 88 and 90. At each end of thebeams 88 and 90, the upper and lower flanges 96 and 98 are cut away, anda plate 100 is welded to each side of the web 102, with a pair ofhorizontally spaced holes 104 and 106 being drilled through plates 100and web 102. The lower ends of the cables 40 are secured to the insidehole 106, with the length of all the cables 40 being equal between thepoints of attachment on the crosshead and on the platform. By reason ofthis suspension arrangement of crosshead 42, platform 36, and cables 40,the platform 36 will always remain parallel to the crosshead 42 and willnot tip or tilt even when the weight thereon due to equipment, menand/or debris is unevenly distributed or suddenly shifted. The stabilityof the platform 36 is further enhanced by the fact that the intersection66 of the beams 62 and 64, the intersection 94 of the beams 88 and 90and the vertical axis of the grab ring 50 all lie substantially on acommon vertical line.

Referring now to FIGS. 2 and 2A, one end of a relatively short wire ropeor cable 108, called a igtail, is secured to the outside hole 104drilled in the ends of platform beams 88 and 90. The other ends of thesefour pigtails are clamped to each of four wire ropes or cables 110 by aplurality of conventional commercially available clamps 112, which arepositioned above the platform 36 so that a workman standing thereon canloosen or tighten the clamps without difficulty.

The four steel cables 110 are attached at their upper ends by cableanchor means 114 to a top ring 116 mounted on the throat of blastfurnace 22. These anchor means 114 are spaced at 90 intervals about theupper flange 118 of top ring 116 and comprise two C-shaped members 120and 122 which engage the outside edge of top ring flange 118. Members120 and 122 are bolted to plates 124 and 126 which sit on the uppersurface of the flange 118. The inner ends of the plates form a yoke 128for receiving the upper end of the cable 110 as it passes around theupper, inside edge of the flange 118. A conventional wire rope or cablesocket 130 for receiving and anchoring the upper end of the cable 110 isheld between the upper ends of the plates 124 and 126 by the pin or bolt132.

The cables 110 extend from the anchor means 114 to the bottom of thefurnace. The lower ends of the cables may hang loosely, but preferablyare extended through holes in the furnace wall, such as through thetuyere 34, and are secured to a furnace column 32. Securing the lowerends of the cable 110 to the furnace superstructure minimizes swingingof the platform 36 within the furnace. Alternatively, wooden outriggers(not shown) can also be utilized to prevent the platform from swingingexcessively. The pigtails 108 support the platform 36 and diggingmachine 38 within the furnace 22 at various vertical positions forteardown operations.

As stated above, the pair of spliced steel I-beams 88 and 90 are theprimary supporting members of the platform 36. Four relatively shortsteel I-beams 138, 140, 142

and 144 are welded between and interconnect the beams 88 and 90, formingan inner square as shown particularly in FIGURE 5. Four additional steelI-beams 146', 148, 150 and 152 are also welded between and interconnectthe beams 88 and 90 forming an outer concentric square, as shown in FIG.5. For added strength, four L-shaped reinforcing members 154, 156, 158and 160 are fastened between the midpoints of beams 138-144 and beams146-152 respectively, as shown in FIG. 5.

The area between the inner square formed by beams 138-144 and the outersquare formed by beams 146- 152 is covered by thick, wooden planking,shown generally at 162. This planking is fastened to the main platformcross/beams 88 and 90 and the described platform members 138, 140, 142,144, 146, 148, 150, 152 and 160 by a plurality of bolts and nuts, theheads of bolts 161 being countersunk in the planking 162 to provide asmooth upper platform surface. As shown in FIG. 9, a piece of Wood ormetal 164 is placed between the upper surface of the members 154-160 andthe planking to compensate for the thickness of the I-beam flanges.

As shown in FIG. 5, the above desiribed generally square base portion ofthe platform may be enlarged by attaching supplementary sections 166,168, 170 and 172 to its sides, whereby the platform 36 assumes agenerally circular shape having a diameter equal to the length of themain beams 88 or 90.

The primary supporting members for each of sections 166-172 are threelike triangular braces 174, 176 and 178. These triangular braces aremounted between the upper and lower flanges of the beams 14 6-152; and,as shown in FIGS. 6 and 7, they are attached thereto by long bolts 180which pass through aligned holes drilled in the upper and lower flangesof beams 146-152 and in the upper and lower extensions 179 and 181forming part of the braces. The braces can be pivoted about the bolts180 whereby they either project from the sides of the beams 146-152, asin FIG. 5, or are swung so that they lie adjacent the web 182 of theI-beams 14 6-152. The braces are placed in this latter position when notin use. But, if it is desired to enlarge the surface of the platform 36,the braces are swung out to the positions shown in FIG. 5, and heavywooden planking 184, similar to 162, is laid over the braces andfastened to the braces, preferably by countersunk bolts. Pieces of woodor metal 186 are placed between planking 184 and braces 174-178 tocompensate for the thickness of the I-beam flanges.

Thus, when the supplementary sections 166-172 are used, the uppersurface platform 36 is covered by relatively smooth, uninterruptedplanking except for a small area at each end of the main members 88 and90 and the center square bounded by the four I-beams 138-144, over whichthe digging machine 38 is mounted, as now discussed.

As shown in FIG. 5, four mounting plates 188, 190, 192 and 194 arefastened to the platform 36 at the junc tures of beams 88 and 90 withbeams 138-144. A bottom plate 196 is also fastened to the platform 36 bya plurality of bolts, and overlies the mounting plates 188-194 and thecentral area bounded by the four beams 138-144. In practice, the samebolts secure both the mounting plate and the bottom plate to the plaform36, alhough, of course, this is not necessary.

Referring especially to FIGURE 10, there is mounted on the bottom plate196 a lower portion 198 of the housing of -a heavy weight thrust bearing200 which is of conventional commercially available design. The upperportion 202 of this bearing housing is attached to the bottom of thedigging machine 38. The outer ring 205 of the bearing 200 is providedwith a gear 206, and the ring 205 is secured to the plate 198 and thusthe platform 36. This gear 206 which is part of the commercial bearing200 is utilized to prevent the digging machine 38 from rotating relativeto the platform 36 when the lock- 6 ing mechanism 208 is engaged. Thismechanism 208, shown in FIGS. 10 and 11, comprises a handle 210 whichcan be actuated by the operator of the machine and which is attached toa vertical shaft 212 extend-ing downwardly through a guide 214 to thehorizontal plane of the gear 206. The lower end of the shaft 212 isconnected to a crank 216, which through link 218, is connected to a lock220 supported and guided by a lock guide 222 and slide bearing 224. Themechanism 208 is arranged so that movement of the handle 210 in onedirection causes the lock 220 to advance towards the gear 206 andintermesh with the teeth thereof, thus preventing the machine 38 fromrotating relative to platform 36. Movement of the handle 210 in theopposite direction causes the lock 220 to move away from the gear 206and allows the machine 38 to rotate freely with respect to platform 36.

The digging machine 38 is mounted on the platform 36 such that thecenters of gravity of the machine and the platfrom lie on a commonvertical line. The machine 38 is basically a conventional hydraulicexcavator unit comprising motor 226, pump (not shown), operatorscontrols 228, boom 230, stick 232, and tool 234, etc. The Hopto Model220TM excavator manufactured and sold by Warner & Swasey of Cleveland,Ohio, and similar excavators made by International Harvester Company andothers may be used for digging machine 38, with minor modifications ofthe commercial model. For example, due to space limitations andenvironment, the conventional gasoline or diesel engine is replaced by acompact 220 or 440 volt electric motor, and the engine mounting portionshortened to permit rotation on a smaller diameter platform.

Assuming use of a Hopto Model 220TM, the machine 38 has a hydraulicallyactuated boom 230, stick 232, and tool mount 240. The boom 230 can beswung through a working arc of about 200 degrees, independent of anymovement of the machine itself; and the tool 234 pivoted about the endof the stick 232 through an angle of about 165 degrees. The boom, stickand tool can be brought in close to the center of the platform so thatthe boom can be swung through an arc of more than degrees withouthitting the cables 40, 108, or 110.

The tool 234, includes a standard commercial air hammer 236, forexample, the Ingersoll Rand Buster Model X-72, with a moil 238, attachedthereto. The length of the moil may be between 1-6 feet, and preferablyis 2 feet.

The air hammer 236 and moil 238 are mounted along the base of atriangular bracket 240 of U-shaped crosssection, which may be attachedto the end of the stick 232 in either of two positions. As shown in FIG.12, the bracket 240 is attached apex up to the hydraulic motor means 242at the angle opposite the base which is pivotedly attached at one end tothe end of the stick itself. When mounted in this manner, the moil 238is generally directed or pointed upward. As shown in FIG. 13, thebracket 240 can also be attached apex down to the stick at the angleopposite the base, which is secured at one end to the motor means 242.When attached in this manner, the moil 238 is generally directed or:pointed downward. The orientation of bracket 240 on the stick 232 canbe easily changed While the machine is in the furnace to modify theWorking angle of air hammer moil 238.

Since the total reach of the boom and stick of the Hopto Model ZOOTM isapproximately 19 feet plus the length of the moil, it is apparent thatthe machine 38 is capable of tearing down the lining in all but thelargest blast furnaces. However, if the radius of the furnace is largerthan the combined reach of the boom, stick and moil, the platform 36 canbe shifted off-center and held there by guy lines or suitable Outriggers(not shown) extending from platform 36. The suspension system 44 is suchthat even in this off-center position, the platform remains parallel tothe ground, and operation is stable.

The extensible boom permits the machine 36 to be mounted in the centerof the platform throughout the entire teardown operation and thus thevertical loading always remains substantially the same. Furthermore,there is no need to modify or enlarge the platform 36 as the teardownoperation progresses down the ever-increasing diameter furnace 22, asheretofore required.

Operation After the furnace, whose lining is to be torn down andreplaced, has cooled sufficiently the anchor means 114 and the cables110 are installed in the furnace. If the throat of a furnace is largeenough, the crosshead 42, platform 36, and digging machine 38 arelowered as a unit directly into the furnace to the proper level and thepigtails 108 attached to the cables 11%. However, if the throat isnarrow, the digging machine 38 and the peripheral platform sections166-172 are removed so that platform 36 may itself be lowered sidewaysinto the furnace, and then leveled so that the pigtails 108 can beattached to the cables 110. Once the platform is in the furnace thecrosshead 42 is suspended over the platform and the cables 40 areconnected between the platform and crosshead. Next the machine 38 andalso platform sections 166472 are remounted on the platform 36.

The platform is supported by the pigtail 108 and the cables 110, andbears the load imposed when the air hammer moil 238 is applied to thefurnace lining 26 to break it away from shell 24, as shown in. FIG. 12or in FIG. 13. In general practice, the lining is torn down proceedingfrom the top of the furnace to the bottom and the platform is usuallysuspended at, or slightly above, the level of the remaining lining toprevent pieces of brick etc. from striking the workmen on the platform.The digging machine 36 and air hammer 236 are operated in conventionalmanner as will be apparent to those in the art in light of thedisclosure herein. The moil 238 is operated in downward direction to theextent feasible, to load cables 110 vertically.

When it is desired to lower or raise the platform 36 and machine 38within the furnace 22, as when all the lining 26 has been removed at agiven level, the clamps 112 are loosened and the platform is accordinglyraised or lowered by the hoist 46 through the suspension system 44. Theclamps 112 are then retightened, at the new vertical level and themachine can again begin tearing down the lining. When it is desired torotate the machine, as for example to teat-down the opposite side of thefurnace, the moil 238 is securely embedded in the brick lining 2-6, withthe boom and stick extending between two cables. The lock mechanism 208is released, and the actuating means for boom 230 is operated, therebycausing the machine 38 to rotate up to 200 relative to platform 36 sincethe tool and boom are fixed. Thereafter, the gear 206 is again lockedagain-st rotation of machine 38, and the boom, stick and moil areretracted within the cables 40 and 110 (see dotted line in FIGURE 12),and the boom is swung past the cables to relocate the moil for continuedteardown operation. If further rotation of the machine is desired, thisprocedure is repeated.

A further advantage of the above-described crosshead 42, cables 40 andplatform 36 arrangement is that the boom, etc. of the machine 36 can beswung through a full 90 degree are before it contacts one of the cables,and the machine 36 can be rotated through 360 degrees relative to theplatform.

While the apparatus of this invention can, of course, be constructed invarious sizes, in the preferred embodiment, the beams 83 and 90 of theplatform and the beams 62 and 64 of the crosshead are 15 feet in lengthand the other parts of the apparatus are scaled accordingly.

It is apparent from the foregoing that the new improved blast furnaceteardown apparatus of this invention provides quicker and more efficientremoval of the linings of blast furnaces than was possible withapparatus and methods heretofore used; that the apparatus of thisinvention is safer than prior systems; that this system requiressignificantly fewer men and total man-hours to do a superior job; thatthe new system of this invention is flexible and adaptable to differentsize blast furnaces; and that the present invention achieves variousobjectives, advantages and improved results as set forth earlier in thisapplication.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. An improved apparatus for tea-ring down the lining in the shell of ablast furnace comprising: a platform; means for raising and loweringsaid platform within a furnace; means for stabilizing the platform at adesired location; and power operated teardown means rotatably mounted onsaid platform and capable of tearing down the lining of said furnacethroughout its circumference, said second recited means including aplurality of elongated cables secured to an upper portion of the furnaceand extending towards the bottom thereof, with means attached to saidplatform for connecting the platform with said elongated cables.

2. An apparatus as defined in claim 1 wherein the lower ends of saidelongated cables pass through apertures in the furnace walls and aresecured externally of the furnace shell.

3. In combination, an apparatus for tearing down the lining in a blastfurnace comprising: a platform adapted to pass through the throat ofsaid furnace; cable means secured to an upper portion of the furnace andextending toward the bottom of the furnace; means for connecting saidplatform to said cable means whereby said platform may be supported atdesired vertical position within said furnace; hoist means for raisingand lowering said platform in said furnace including a crossheadpositioned above and connected with said platform by a plurality ofcables of substantially equal length; and a power operated diggingmachine mounted on the top surface of said platform, said platformhaving substantially a square shape and including two main beams splicedtogether, with two sets of shorter beams interconnecting said mainbeams, one set being near said intersection of said main beams and theother set being adjacent the ends of said main beams, supporting bracesinterconnecting the beams of said one set with the beams of said otherset, and planking secured to said beams for covering the area betweenthe said two sets of beams.

4. The combination recited in claim 3 in which brackets are pivotablyattached to the outer.sides of said other set of beams and can becovered with planking so as to extend the platform with a substantiallycircular shape having a diameter equal to the length of said main beams.

5. An improved teardown apparatus for tearinig down the lining in ablast furnace comprising: a platform including a main frame; meanscoupled to said platform for supporting it within a blast furnace;bearing means on the top surface of said main frame; a digging machinehaving an extensible boom mounted on said bearing means above said mainframe, the machine being rotatable with respect to the platform; andlocking means for preventing rotational movement of said machinerelative to said platform; supporting means for raising and loweringsaid platform from within said furnace including a cable extending fromwithout said furnace and connected to a crosshead, said crossheadincluding frame members having portions thereof connected to parts ofthe platform by cables so that said platform is maintained substantiallyparallel to said crosshead; a plurality of elongated cables secured toupper portions of said furnace with their lower ends extending adjacentthe bottom of said furnace, and means for connecting said cable means tosaid platform to support the platform.

6. An improved teardown apparatus for tearing down the lining in a blastfurnace comprising: a platform including a main frame; means coupled tosaid platform for supporting it within a blast furnace; bearing means onthe top surface of said main frame; a digging machine having anextensible boom mounted on said bearing means above said main frame, themachine being rotatable with respect to the platform; locking means forpreventing rotational movement of said machine relative to saidplatform, said platform including main supporting beams, supportingmembers interconnecting said beams, means covering said beams andmembers so that said platform has an unobstructed upper surface, bracespivotaibly and. removably attached to the outer edges of said platformand 10 adapted to project therefrom, and additional means for coveringsaid braces for providing an extension of said platform surface.

References Cited UNITED STATES PATENTS 3,346,300 10/1967 Grant 299703,302,976 2/1967 Grant 29970 748,962 1/1904 Lewis 182142 X 1,067,3757/1913 Proctor 299-70 X 2,346,033 4/ 1944 Jordon 18212'8 2,710,418 6/1955 Putnam. 2,983,496 5/1961 Grant 29970 X 3,090,983 5/1963 Modrak etal. 299-70 X ERNEST R. PURSER, Primary Examiner.

US. Cl. X.R. 17343; 182128 3 5 33 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent 3 L120 Dated April 1 1969 Inventor(s)John Armstrong It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

I" Column 3, line 12 should read along line 3-3 in FIGS.

1 and 2); Column 5, line 63, "alhough" should be altho SIGNED Arw SEALEDDEC 2 19% Axum Flewhe" WILLIAM E. SOHUYL'SR, JR. Attestmg Offic sionerof Patents

1. AN IMPROVED APPARATUS FOR TERARING DOWN THE LINING IN THE SHELL OF ABLAST FURNACE COMPRISING: A PLATFORM; MEANS FOR RAISING AND LOWERINGSAID PLATFORM WITHIN A FURNACE MEANS FOR STABILIZING THE PLATFORM AT ADESIRED LOCATION; AND POWER OPERATED TEARDOWN MEANS ROTATABLY MOUNTED ONSAID PLATFORM AND CAPABLE OF TEARING DOWN THE LINING OF SAID FURNACETHROUGHOUT ITS CIRCUMFERENCE, SAID SECOND RECITED MEANS INCLUDING APLURALITY OF ELONGATED CABLES SECURED TO AN UPPER PORTION OF THE FURNACEAND EXTENDING TOWARDS THE BOTTOM THEREOF, WITH MEANS ATTACHED TO SAIDPLATFORM FOR CONNECTING THE PLATFORM WITH SAID ELONGATED CABLES.